Every table in the star schema except the fact table has a parent
table, and a condition which specifies how it is joined to its parent.
So the star schema is, in effect, a hierarchy with the fact table at
its root.

makeMeasure

makeColumns

This is only called by RolapCube. If the RolapLevel has a non-null
name expression then two columns will be made, otherwise only one.
Updates the RolapLevel to RolapStar.Column mapping associated with
this cube.

Parameters:

cube - Cube

level - Level

parentColumn - Parent column

addJoin

Extends this 'leg' of the star by adding relation
joined by joinCondition. If the same expression is
already present, does not create it again. Stores the unaliased
table names to RolapStar.Table mapping associated with the
input cube.